摘要:

A review of the theories of light ion flow from the polar cap in their hydrodynamic and evaporative forms is offered. Both types of theories should be able to provide correct treatments of the phenomenon. Some difficulties with the hydrodynamic theory are mainly interpretative and should disappear if the so‐called pressure gradient force term in the equations of motion is recognized as really inertial in nature. An important new insight has been provided recently in an evaporative theory by the realization that the electric field in the exosphere required to balance electron and ion fluxes is quite different from the electric field of gravitational separation usually used in ionospheric theory. However, an evaporative theory that is based on realistic boundary conditions as well as an acceptable electric field remains to be worked out. The situation in the polar ionosphere is sufficiently complex that experimental studies will undoubtedly be needed to establish the actual conditions that exist ther

ISSN:8755-1209    

DOI:10.1029/RG009i001p00001

年代:1971

数据来源: WILEY

摘要:

The nonadiabatic motion of geomagnetically trapped particles acrossLshells has been inferred from the measured distributions of trapped particles and has also been observed directly in a number of cases. This type of motion has important influences on both the steady‐state structure and the dynamics of the radiation belts. The characteristics of the radial motion have been evaluated and are generally consistent (within an order of magnitude) with the radial diffusion expected from fluctuations in the magnetospheric electric and/or magnetic fields. However, the complexity and variability of the observed phenomena suggest that several basic processes are acting simultaneously, and further efforts are needed to identify specific mechanism

ISSN:8755-1209    

DOI:10.1029/RG009i001p00011

年代:1971

数据来源: WILEY

摘要:

This paper presents a coherent exposition of the modern statistical theory of the transport of fast charged particles (cosmic rays) in the solar wind. Observations are discussed only as they illustrate the phenomena under discussion. A brief introductory section surveys the historical development of the theory. The dominant effect on the motion of cosmic rays in the solar wind is the interplanetary magnetic field, which is irregular and which is therefore best treated statistically, using random functions. The magnetic irregularities scatter the cosmic rays in pitch angle, so that to a good approximation the cosmic rays diffuse through the irregular magnetic field. Using a statistical analysis of the equations of motion, one may relate the diffusion tensor to the power spectrum of the magnetic field, which is in principle measurable. The resulting general transport theory relates the motion of cosmic rays, statistically, to the solar‐wind velocity and magnetic field. Application of the theory both to the modulation of galactic cosmic rays by the solar wind and to the propagation of solar cosmic rays is discussed in detail. It is concluded that the present theory explains the principal phenomena quite well. Future theoretical work will probably be devoted to obtaining better solutions of the equations, to obtaining better values of the parameters, and to studying higher‐order or more subtle effe

ISSN:8755-1209    

DOI:10.1029/RG009i001p00027

年代:1971

数据来源: WILEY

摘要:

Theoretical work and observations on extraterrestrial Lyman α are reviewed. A source of extraterrestrial Lyman α near the solar apex is probably scattering of solar Lyman α on cold interplanetary hydrogen that has penetrated to the inner solar system. A minor source of interplanetary hydrogen comes from the breakup of comets. Galactic sources of Lyman α are probably also present, and such emission would tend to be rendered isotropic, depending on the amount of interstellar hydrogen in the near vicinity of the solar sys

ISSN:8755-1209    

DOI:10.1029/RG009i001p00089

年代:1971

数据来源: WILEY

摘要:

A region‐by‐region analysis of 204 reliable focal‐mechanism solutions for deep and intermediate‐depth earthquakes strongly supports the idea that portions of the lithosphere that descend into the mantle are slablike stress guides that align the earthquake‐generating stresses parallel to the inclined seismic zones. At intermediate depths extensional stresses parallel to the dip of the zone are predominant in zones characterized either by gaps in the seismicity as a function of depth or by an absence of deep earthquakes. Compressional stresses parallel to the dip of the zone are prevalent everywhere the zone exists below about 300 km. These results indicate that the lithosphere sinks into the asthenosphere under its own weight but encounters resistance to its downward motion below about 300 km. Additional results indicate contortions and disruptions of the descending slabs; however, stresses attributable to simple bending of the plates do not seem to be important in the generation of subcrustal earthquakes. This summary, intended to be comprehensive, includes nearly all solutions obtainable from the World‐Wide Standardized Seismograph Network (WWSSN) for the period 1962 through part of 1968 plus a selection of reliable solutions of pre‐1962 events, and it includes data from nearly every region in the world where earthquakes occur in the mantle. The double‐couple or shear dislocation model of the source mechanism is adequate f

ISSN:8755-1209    

DOI:10.1029/RG009i001p00103

年代:1971

数据来源: WILEY

摘要:

If a long earthquake sequence is considered to be a stationary stochastic process, the stored elastic energy of deformation can be shown to be an independent variable in the usual ‘backward’ equation. Three unknown probability functions are introduced: the probability that the stored energy of deformation is at a certain level; the probability that, if this energy is at a given level, an earthquake will occur; and the transition probability that, if the earthquake occurs, the final energy state will be at a certain level. It is assumed that the frequency‐energy distribution is known. The equations can be solved, if the transition probability is assumed to be known; and they have been solved for the model in which the transition probability is a function of the energy released in the shock but is not otherwise dependent on the final energy state. In this case, the results can be used to describe the earthquake history for some time after a great shock, and possibly for times just before a great shock. The results have some features of inconsistency with observa

ISSN:8755-1209    

DOI:10.1029/RG009i001p00175

年代:1971

数据来源: WILEY